Non-pathological lower back pain, i.e., back pain associated with weakness, inhibition, wasting, misfiring/mistiming or abnormalities of the muscles that support the trunk rather than secondary to cancer, infection, fractures, etc., is a leading cause of morbidity, sick leave and physician consultations.
Contributory factors include inhibition of muscle activity (perhaps secondary to the pain itself), inability of the patient to voluntarily control the specific muscles and appropriately perform rehabilitation exercises, and lack of compliance with the exercise regimes.
These muscles include multifidus, the obliques and transversus abdominis. It is thought that the deep fibres of multifidus are especially important in stabilising the spine. These muscle fibres have been historically difficult to recruit and train through traditional techniques including the following:
(a) Voluntary exercises (with or without equipment).
These are difficult to do properly, especially without the attendance of (expensive) trained personnel. The muscle itself may not be properly recruited. Compliance may be poor. Results are variable.
(b) Transcutaneous electrical nerve stimulation (TENS).
TENS is a form of symptomatic relief. The hope is that with reduced pain the muscle may begin to function normally again alleviating the on-going pain. Studies suggest that the a third of people get substantial relief, a third improve somewhat and the remaining get little benefit.
(c) Implanted stimulation techniques.
These are, by their nature, invasive and have not been shown to have clear benefit beyond other techniques for a typical patient.
(d) Neuromuscular electrical stimulation (NMES).
NMES has been around for many decades. It is not routinely used in the treatment of lower back pain because it has not been shown to have therapeutic benefits beyond TENS. The NMES used tends to cause contraction of relatively superficial muscle fibres of the lower back and not target the deep muscle fibres where a lot of the supporting and stabilisation of the back is thought to occur. Usually the current travels between pads placed on the lower back. Because the current is substantially travelling through one plane, i.e. in line with the skin, the current tends not to travel deeply at the intensities required to stimulate deep fibres.
In addition because it is uncomfortable to selectively stimulate the lower back (in comparative isolation) the contractions tend to be painful and may cause hyperextension of the lower back. This limits the current intensity thus the likelihood of direct stimulation of the deep paraspinal fibres is less likely. The abdominal musculature tends to be less activated, hence receives less training and the inner fibres supporting the spine remain comparatively inactive.
Additionally, although the pulses and pad positions may be balanced with traditional NMES, the resulting muscle contraction may be imbalanced. This may be due to greater muscle weakness on one side—a common finding in lower back pain. This may cause potentially harmful skewing of the patient.
U.S. Pat. No. 4,381,012, Russek discloses a TENS belt with electrodes located close to the spine and electrodes more lateral to the spine. However, Russek is not an effective lower back pain treatment, nor an advance on standard therapies, merely away to apply standard therapies. The suggested positions are for TENS and the use of the set up at a user tolerable and safe level would not elicit contractions of the deep multifidus fibres.
The high prevalence of chronic lower back pain suggests that the current therapeutic approaches are insufficient in some way. It is an object of the invention to provide an improved method and apparatus for treating lower back pain.